The purpose of this project is to perform basic immunological studies in mink infected with the Aleutian disease virus ADV, a nondefective parvovirus. In the past year, a sensitive solid phase radioimmunoassay for ADV antigen and anti-ADV antibodies was developed. The assay could detect approximately 3.2 ng of ADV protein. After experimental infection, antigen could be detected in gut and kidney at days 3-6 and by day 10 antigen was localized in spleen, liver, kidney, lymph nodes, as well as peritoneal exudates and bone marrow cells. Quantitation was confounded by antibody being present in samples after day 6. In addition, using inhibition of binding, a sensitive assay for anti-ADV antibody was developed capable of detecting as little as 5 ng of antibody. Antibody could be detected as early as 3 days after infection and titers up to 1/106 were found in infected mink. Utilizing this RIA for antibody, several important studies were performed: 1) The amount of anti-ADV antibody in hypergammaglobulinemic sera was calculated and found to be from 13-57% of the total gammaglobulin fraction, indicating a polyclonal stimulation of Ig synthesis in infected mink, 2) The affinity of antiviral antibodies from a number of pooled and individual sera was determined to be indicative of high quality antibody, suggesting that the virus-antiviral antibody complexes in AD are caused by high, not low, affinity antibody and, 3) Estimates of the heterogeneity of antiviral antibodies in these same sera suggested that some, but not all, infected mink develop antibodies of restricted heterogeneity; in fact some were as homogeneous as monoclonal antibodies.